<HTML>
<!--
     Copyright (c) Jeremy Siek, Lie-Quan Lee, and Andrew Lumsdaine  2000

     Distributed under the Boost Software License, Version 1.0.
     (See accompanying file LICENSE_1_0.txt or copy at
     http://www.boost.org/LICENSE_1_0.txt)
  -->
<Head>
<Title>Boost Graph Library: Visitor Concepts</Title>
<BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b"
        ALINK="#ff0000">
<IMG SRC="../../../boost.png"
     ALT="C++ Boost" width="277" height="86">

<BR Clear>

<H1><A NAME="sec:visitor-concepts"></A>
Visitor Concepts
</H1>

<P>
The visitor concepts plays the same role in BGL as <a
href="http://www.boost.org/sgi/stl/functors.html">functors</a>
play in the STL. Functors provide a mechanism for extending an
algorithm; for customizing what is done at each step of the algorithm.
Visitors allow the user to insert their own operations at various
steps within a graph algorithm. Unlike the STL algorithms, graph
algorithms typically have multiple event points where one may want to
insert a call-back via a functor. Therefore visitors do not have a
single <tt>operator()</tt> method like a functor, but instead have
several methods that correspond to the various event points. Each
algorithm has a different set of event points, which are described by
the following visitor concepts:

<ul>
  <li> <a href="./BFSVisitor.html">BFS Visitor</a>
  <li> <a href="./DFSVisitor.html">DFS Visitor</a>
  <li> <a href="./DijkstraVisitor.html">Dijkstra Visitor</a>
  <li> <a href="./BellmanFordVisitor.html">Bellman Ford Visitor</a>
  <li> <a href="./AStarVisitor.html">A* Visitor</a>
  <li> <a href="./EventVisitor.html">Event Visitor</a>
  <li> <a href="./PlanarFaceVisitor.html">Planar Face Visitor</a>
  <li> <a href="./TSPTourVisitor.html">TSP Tour Visitor</a>
</ul>


<br>
<HR>
<TABLE>
<TR valign=top>
<TD nowrap>Copyright &copy; 2000-2001</TD><TD>
<A HREF="http://www.boost.org/people/jeremy_siek.htm">Jeremy Siek</A>,
Indiana University (<A
HREF="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</A>)<br>
<A HREF="http://www.boost.org/people/liequan_lee.htm">Lie-Quan Lee</A>, Indiana University (<A HREF="mailto:llee@cs.indiana.edu">llee@cs.indiana.edu</A>)<br>
<A HREF="https://homes.cs.washington.edu/~al75">Andrew Lumsdaine</A>,
Indiana University (<A
HREF="mailto:lums@osl.iu.edu">lums@osl.iu.edu</A>)
</TD></TR></TABLE>

</BODY>
</HTML>
